A piezoelectric driving precision micro-gripper with two degrees of freedom force and three degrees of freedom pose measurement and use method

Abstract

A two-degree-of-freedom force and three-degree-of-freedom pose measurement piezoelectric drive precision micro-gripper and use method, belong to micro assembly robot field, including clamping module, clamping force measurement module, positioning and assembly force measurement module, optical fiber sensing module, base, precision device, its directly above is equipped with the plane to be assembled.The clamping module is arranged on the positioning and assembly force measurement module, and is used for generating ideal displacement output;The clamping force measurement module is arranged on the clamping module, is located in the middle of its compliant amplification structure, and is used for measuring the size of clamping force;The positioning and assembly force measurement module, optical fiber sensing module are arranged on the base, and the optical fiber sensing module is used for measuring pose;The positioning and assembly force measurement module is used for ensuring positioning accuracy and measuring assembly force.The application can ensure reliable clamping and positioning of precision device during assembly process, prevent the case that precision device is damaged due to too large displacement change, and realize high-precision precision assembly requirement.

Description

Technical Field

[0001] This invention belongs to the field of micro-assembly robots and relates to a piezoelectrically driven precision micro-gripper for two-degree-of-freedom force and three-degree-of-freedom pose measurement and its usage method. Background Technology

[0002] With the continuous advancement of technology, high precision and miniaturization have become key development trends in modern high-tech fields. Against this backdrop, fields such as micro-assembly, ultra-precision machining, microelectronics, microelectromechanical systems, precision optics, aerospace, and robotics are placing increasingly higher demands on the performance of precision micro-grippers.

[0003] Micro-assembly of precision components is a current research hotspot in the field of micro-assembly. Since most precision components are fragile, excessive clamping or assembly forces can cause damage, while insufficient forces prevent effective clamping or assembly. Therefore, there are extremely stringent requirements for the clamping and assembly forces of precision micro-grippers. However, current precision micro-grippers still suffer from problems such as low magnification, lack of effective real-time accurate detection of position / clamping force / assembly force, and unsatisfactory overall performance. For example, Chinese invention patent CN115008438A discloses a parallel-output piezoelectric-driven micro-gripper and its control method, which eliminates parasitic displacement along the Y-axis when the clamping arm extends in the piezoelectric stack, improving the accuracy of the clamping action, but lacks a positioning device and has a low magnification. Similarly, Chinese utility model patent CN202622796U discloses a piezoelectric-driven micro-gripper for precision assembly, which increases clamping force sensing, but the magnification is still relatively low, and the lack of a positioning device prevents real-time accurate detection of position / clamping force / assembly force. Summary of the Invention

[0004] To address the problems of low magnification and lack of effective real-time accurate detection of position / clamping force / assembly force in existing precision micro grippers, this invention provides a piezoelectric-driven precision micro gripper and its usage method for two-degree-of-freedom force and three-degree-of-freedom pose measurement. This ensures reliable clamping and positioning of precision components during assembly, while preventing damage to precision components due to excessive force caused by excessive displacement changes. It achieves high-precision assembly requirements and meets the current assembly requirements for precision components in the field of micro-assembly robots.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a piezoelectrically driven precision micro-gripper for measuring two degrees of freedom of force and three degrees of freedom of pose, the piezoelectrically driven precision micro-gripper includes a clamping module 1, a clamping force measuring module 2, a positioning and assembly force measuring module 3, an optical fiber sensing module 4, a base 5, and precision components 6. A plane 7 to be assembled is provided directly above the piezoelectrically driven precision micro-gripper. Using a right-hand coordinate system, the positive X-axis is the direction along the piezoelectric actuator 12 pointing towards the pre-tightening screw 15 in the clamping module 1, and the positive Y-axis is the direction perpendicular to the positioning platform 26 in the positioning and assembly force measuring module 3. The V-groove positioning structure 23 is oriented in the positive Z-axis direction, with the positive X-axis defined as left, the positive Y-axis as up, and the positive Z-axis as front. The clamping module 1 is mounted on the positioning and assembly force measurement module 3 and is located behind it. The clamping force measurement module 2 is mounted on the clamping module 1 and is located between the two leaf-shaped guide mechanisms 19 based on leaf hinges in the compliant amplification structure 8 of the clamping module 1. The positioning and assembly force measurement module 3 is mounted on the base 5. The precision device 6 is mounted on the positioning platform 26 of the positioning and assembly force measurement module 3. The fiber optic sensing module 4 is mounted on the base 5 and is located to the left of the positioning and assembly force measurement module 3. The clamping module 1 is used to generate an ideal displacement output at the end of the clamp in the target output direction during clamping operations; the clamping force measurement module 2 is used to measure the magnitude of the clamping force, reducing the risk of damage to the precision component 6 due to overload; the fiber optic sensing module 4 is used to measure the pose of the plane to be assembled 7 relative to the fiber optic plane, enabling the precision component 6 to fit more precisely and tightly; the positioning and assembly force measurement module 3 is used to ensure the positioning accuracy of the precision component 6 and measure the magnitude of the assembly force, reducing the risk of damage to the precision component 6 due to overload. Specifically:

[0006] The clamping module 1 is primarily a compliant amplification structure 8. Specifically, the compliant amplification structure 8 is an integrated structure consisting of a bridge-type drive mechanism 9 and two U-shaped guide mechanisms 19 based on leaf-shaped hinges. The end of the U-shaped guide mechanism 19 is defined as the front end, and the end of the bridge-type drive mechanism 9 is defined as the rear end. The two U-shaped guide mechanisms 19 are symmetrically distributed about the Y-axis. The front ends of the two U-shaped guide mechanisms 19 are provided with symmetrical screw holes for bolt connection and fixation to the outer screw holes at both ends of the arrow of the positioning and assembly force measurement module 3.

[0007] Furthermore, the bridge-type drive mechanism 9 includes a front parallelogram mechanism 17, a rear parallelogram mechanism 10, a piezoelectric brake 12, a gasket 13, a first flexible hinge structure 16, a preload screw 15, and two end block structures 14. The two end block structures 14 are located at both ends, with a piezoelectric brake 12 in the middle. Gaskets 13 are provided at the contact points between the piezoelectric brake 12 and the end block structures 14, and are fixed by the preload screws 15. Thus, the end block structures 14, piezoelectric brakes 12, and gaskets 13 at both ends of the bridge-type drive mechanism 9 together form an I-shaped structure. The piezoelectric brake 12 provides initial driving force and displacement for the movement of the piezoelectrically driven precision micro-gripper, and the gaskets 13 prevent damage to the end face of the piezoelectric brake 12 due to concentrated load caused by the preload screws 15 during preload. The front parallelogram mechanism 17 and the rear parallelogram mechanism 10 are located between the two end block structures 14 and are symmetrically arranged on both sides of the piezoelectric brake 12 along the X-axis. The front parallelogram mechanism 17 is close to the zigzag guide mechanism 19 and includes four blocks. The middle part is a T-shaped block 18 composed of long and short sides. The four blocks are arranged in pairs and symmetrically arranged on both sides of the short side of the T-shaped block 18. One end of the block is connected to the end block structure 14, and the other end is internally connected to the T-shaped block 18. Each block is doubly connected through the first flexible hinge structure 16. The two ends of the long side of the T-shaped block 18 are respectively connected to the Z-shaped guide mechanism 19; the rear parallelogram mechanism 10 includes four blocks and a middle cuboid block 11. The four blocks are arranged in pairs, symmetrically at both ends of the middle cuboid block 11. One end of the block is connected to the end block structure 14, and the other end is internally connected to the middle cuboid block 11. Each block is doubly connected through the first flexible hinge structure 16; the parasitic motion generated by the front parallelogram mechanism 17 and the rear parallelogram mechanism 10 during movement can cancel each other out, which is used to make the end of the clamping module 1 generate an ideal displacement output in the target output direction; the Z-shaped guide mechanism 19 is used to realize a reliable guiding function, and can also effectively reduce the adverse effects of unnecessary displacement at the output end caused by the asymmetrical deformation of the input end of the gripper due to the action of the pre-tightening screw 15.

[0008] The clamping force measurement module 2 includes a fixed guide beam 20 and a clamping force measuring strain gauge 21. The fixed guide beam 20 is an integrated structure with a thin cuboid block structure in the middle and thick cuboid block structures on both sides. The thin cuboid block structure and the thick cuboid block structures on both sides are doubly connected by a second flexible hinge structure 22. The clamping force measuring strain gauge 21 is attached to the lower part of the second flexible hinge structure 22 and is used to measure the clamping force. The second flexible hinge structure 22 is an over-constrained parallelogram hinge structure composed of two pairs of leaf-shaped flexible hinges. While retaining the "translational output" characteristics of the parallelogram mechanism, it improves the stiffness, stability and motion accuracy of the mechanism through redundant constraints. The clamping force measurement module 2 is located at the front end of the clamping module 1, between the two Z-shaped guide mechanisms 19. Each of the thick cuboid block structures at both ends of the fixed guide beam 20 has a screw hole, which is connected to the long side of the T-shaped block 18 in the compliant amplification structure 8 by screws.

[0009] The positioning and assembly force measurement module 3 is an integrated arrow-shaped structure, including a V-groove positioning structure 23, a force measuring mechanism 24, and a fixing mechanism 25. The V-groove positioning structure 23 and the force measuring mechanism 24 are located on the body of the arrow-shaped structure, the fixing mechanism 25 is located at the arrowhead, the V-groove positioning structure 23 is located at the front end, and the force measuring mechanism 24 is located between the positioning V-groove positioning structure 23 and the fixing mechanism 25. All three are connected by a third flexible hinge structure 27 within the force measuring mechanism 24. Specifically:

[0010] Furthermore, the V-groove positioning structure 23 has a V-groove on the side facing the force measuring mechanism 24. This V-groove, relying on its self-centering characteristics and bidirectional constraint, ensures that the clamping force is uniformly applied to the precision device 6 along a preset direction during clamping, avoiding stress concentration damage to the precision device 6. It also eliminates reference errors caused by positioning offset, improving the positioning accuracy of the precision device 6. The boss structure at the bottom of the V-groove is connected to one end of the third flexible hinge structure 27, and the other end of the third flexible hinge structure 27 is connected to the fixing mechanism 25. The force measuring mechanism 24 includes a positioning platform 26, the third flexible hinge structure 27, and an assembly force measuring strain gauge 28. The assembly force measuring strain gauge 28 is attached to the lower hinge of the third flexible hinge structure 27 for measuring assembly force. The positioning platform 26 is a thin sheet structure with an overall area larger than the precision device 6, used to place the precision device 6 and ensuring uniform force on the precision device 6 during assembly, thus providing a certain degree of protection. The fixing mechanism 25 has two screw holes symmetrically arranged at each end. The two inner screw holes are connected to the base 5 by screws, and the two outer screw holes are connected to the front end of the two Z-shaped guide mechanisms 19 in the clamping module 1 by screws, which serves to fix the mechanism.

[0011] The fiber optic sensing module 4 includes a fiber optic fixing mechanism 29, a reflector 30, and a light probe 31. The light probe 31 is fixed to the rear end groove of the fiber optic fixing mechanism 29 by screws, and the reflector 30 is fixed to the front end groove of the fiber optic fixing mechanism 29 by screws. Specifically, the front end of the fiber optic fixing mechanism 29 is a polygonal beveled surface structure, which forms a groove for placing the reflector 30. The middle part of the fiber optic fixing mechanism 29 is a flat plate structure, with a cube block containing a through hole protruding from the left end of the flat plate structure for fixing the fiber optic sensing module 4 to the base 5. The rear end of the fiber optic fixing mechanism 29 has a block structure, with the bottom of the rear end fixed to the base 5. The middle part of the block structure at the rear end has a groove for placing the light probe 31, and the side of the groove has a through hole. Furthermore, the side of the polygonal beveled surface structure has a screw hole for fixing the reflector with screws.

[0012] A method for using a piezoelectrically driven precision micro gripper for two-degree-of-freedom force and three-degree-of-freedom pose measurement includes the following steps:

[0013] The first step is to place the precision component 6 to be assembled on the positioning platform 26 to complete the pre-assembly step.

[0014] The second step is to perform a clamping operation; the piezoelectric actuator 12 is made to generate a micron-level initial displacement along the Y-axis, and the piezoelectric initial displacement is obtained; the piezoelectric initial displacement is amplified by the compliant amplification structure 8 of the clamping module 1 and transmitted to the end of the piezoelectric driven precision micro-clamping device to obtain the target displacement of the end of the piezoelectric driven precision micro-clamping device, and the piezoelectric driven precision micro-clamping device is controlled to move towards the precision device 6 that has completed the pre-positioning until the piezoelectric driven precision micro-clamping device contacts the surface of the precision device 6 and generates an initial clamping force.

[0015] For clamping force measurement, when the precision device 6 is subjected to contact force, the deformation is output by the clamping force measuring strain gauge 21, and the clamping force is measured by connecting to a strain gauge.

[0016] The clamping force is controlled by PID control. Feedback is generated based on the measured clamping force to control the input voltage of the piezoelectric actuator 12, thereby achieving a stable clamping state.

[0017] The third step is to perform fiber optic sensing and positioning before the assembly operation. The light emitted by the light probe 31 is reflected by the reflector 30 to the plane 7 to be assembled. The reflected light returns to the fiber end face through the original path. The optical power is collected and the pose error of the plane 7 to be assembled relative to the fiber plane is calculated. The pose is then finely adjusted so that the precision device 6 can fit tightly with the plane 7 to be assembled.

[0018] The fourth step is to perform precision assembly operations. After the precision component 6 and the assembly plane 7 are in contact, the assembly force measuring strain gauge 28 in the force measuring mechanism 24 is displaced. The assembly force is measured by connecting a strain gauge, and the control is performed based on the measured assembly force.

[0019] Fifth step: After the precision assembly operation is completed, the clamping module 1 releases the precision component 6 by reducing the input voltage to the piezoelectric brake 12, thus completing a single assembly operation.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) As a precision micro gripper, this invention uses a piezoelectric actuator as the driving source for a piezoelectric-driven precision micro gripper with two degrees of freedom force and three degrees of freedom pose measurement. The extension and retraction are controlled by an external voltage, which has good controllability and extremely small displacement (usually in the nanometer to micrometer range). With the help of a closed-loop feedback system, it can achieve positioning accuracy at the nanometer or even sub-nanometer level. The response speed is fast, which can further improve the gripping accuracy and stability of precision instruments. Moreover, the piezoelectric actuator does not require a complex transmission mechanism (such as gears or lead screws) and can directly generate driving force through its own deformation. The structure is simple and compact, making it suitable for use in confined spaces to ensure the assembly quality of precision devices. The compliant amplification structure consists of a bridge-type drive mechanism and two zig-shaped guide mechanisms based on leaf-shaped hinges. The bridge-type drive mechanism consists of two sets of parallelogram mechanisms. The parasitic motion generated by the two sets of parallelogram mechanisms during movement can cancel each other out, resulting in a large amplification factor, so that the end of the gripper produces an ideal displacement output in the target output direction. Due to gravity, piezoelectrically driven precision micro-grippers for two-degree-of-freedom force and three-degree-of-freedom pose measurement will produce vertical displacement, which will be further amplified when gripping objects. Using a zigzag guide mechanism based on leaf hinges can reduce the displacement caused by gravity. In addition, it can also play a certain guiding role, reducing the influence of unnecessary displacement of the output end caused by the asymmetry of the deformation of the gripper input end due to the pre-tightening screw hole.

[0022] (2) The fixed guide beam of the clamping force measurement module of the present invention adopts an integrated structural design. The middle part is a thin cuboid block structure, and the two sides are thick cuboid block structures. The two ends of the cuboid block structures are connected by a second flexible hinge structure, which can reduce the parasitic displacement generated during force measurement. The small displacement generated when under force can achieve passive compliance protection, reducing the risk of damage to the clamped object due to sudden excessive force. The clamping force measurement strain gauges are attached to the two sides below the flexible hinge structure. The clamping force can be indirectly measured by the deformation generated when the strain gauges are under force, thereby solving the problem that precision devices are relatively fragile and excessive clamping force will cause damage to precision devices.

[0023] (3) The positioning and assembly force measurement module of the present invention is an integrated arrow-shaped structure. In terms of positioning, it adopts a V-groove positioning structure, which has good positioning accuracy. The third flexible hinge structure in the force measuring mechanism of the assembly force measurement module is a flexible over-constrained parallelogram mechanism. When subjected to force, it can generate a small displacement to achieve passive compliance protection, reducing the risk of damage to the clamped object due to sudden excessive force. Corresponding assembly force measuring strain gauges are attached to both sides below the flexible over-constrained parallelogram mechanism. The magnitude of the assembly force can be indirectly measured by the deformation generated by the assembly force measuring strain gauges when subjected to force, thereby solving the problem that precision parts are relatively fragile, excessive assembly force will cause damage to precision parts, and insufficient force will cause precision parts to be unable to be effectively assembled.

[0024] (4) In the fiber optic sensing module of the present invention, the light emitted from the transmitting fiber is reflected by the reflector to the plane to be assembled, and the reflected light is received by the receiving fiber at the end face of the fiber via the original path. The optical power of each receiving fiber is collected by the optical power meter, and the position and orientation of the plane to be assembled relative to the fiber plane can be obtained by inverse solution through the mathematical model, so that the precision instruments can be more accurately and tightly fitted.

[0025] In summary, the present invention has a compact structure, a high degree of integration, a large displacement amplification factor, and can realize clamping force, assembly force, and three-degree-of-freedom pose measurement, making it suitable for the field of precision instrument micro-assembly. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the overall assembly of the precision micro gripper of the present invention.

[0027] Figure 2 This is a schematic diagram showing the installation positions of each module of the precision micro gripper of the present invention.

[0028] Figure 3 This is a schematic diagram of the precision micro gripper clamping module of the present invention.

[0029] Figure 4 This is a schematic diagram of the clamping force measurement module of the precision micro gripper of the present invention.

[0030] Figure 5 This is a schematic diagram of the clamping force measurement module of the precision micro gripper of the present invention.

[0031] Figure 6 This is a top view of the precision micro gripper positioning and assembly force measurement module of the present invention.

[0032] Figure 7 This is a side view of the positioning and assembly force measurement module of the precision micro gripper of the present invention.

[0033] Figure 8 This is a schematic diagram of the fiber optic sensing module structure of the precision micro gripper of the present invention.

[0034] In the diagram: 1. Clamping module; 2. Clamping force measurement module; 3. Positioning and assembly force measurement module; 4. Fiber optic sensing module; 5. Base; 6. Precision components; 7. Assembly plane; 8. Compliant amplification structure; 9. Bridge drive mechanism; 10. Rear parallelogram mechanism; 11. Middle cuboid block; 12. Piezoelectric brake; 13. Gasket; 14. End block structure; 15. Preload screw; 16. First flexible hinge structure; 17. Front parallelogram structure; 18. T-shaped block; 19. Z-shaped guide mechanism; 20. Fixed guide beam; 21. Clamping force measurement strain gauge; 22. Second flexible hinge structure; 23. V-groove positioning structure; 24. Force measuring mechanism; 25. Fixing mechanism; 26. Positioning platform; 27. Third flexible hinge structure; 28. Assembly force measurement strain gauge; 29. ​​Fiber optic fixing mechanism; 30. Reflector; 31. Light probe. Detailed Implementation

[0035] The detailed technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0036] A piezoelectrically driven precision micro-gripper for two-degree-of-freedom force and three-degree-of-freedom pose measurement, such as Figure 1 As shown, the piezoelectric-driven precision micro-gripper includes a clamping module 1, a clamping force measurement module 2, a positioning and assembly force measurement module 3, an optical fiber sensing module 4, a base 5, and precision components 6. A surface 7 to be assembled is located directly above the piezoelectric-driven precision micro-gripper. Using a right-hand coordinate system, the positive X-axis is defined as the direction from the piezoelectric actuator 12 to the pre-tightening screw 15, the positive Y-axis is perpendicular to the positioning platform 26, and the positive Z-axis is perpendicular to the piezoelectric actuator 12 to the V-groove positioning structure 23. The positive X-axis is defined as left, the positive Y-axis as top, and the positive Z-axis as front. The clamping module 1 is mounted on the positioning and assembly force measurement module 3, located behind it. The clamping force measurement module 2 is mounted on the clamping module 1, located between the two zig-shaped guide mechanisms 19 based on leaf hinges in the compliant amplification structure 8 of the clamping module 1. The positioning and assembly force measurement module 3 is mounted on the base 5. The precision device 6 is mounted on the positioning platform 26 of the positioning and assembly force measurement module 3. The fiber optic sensing module 4 is mounted on the base 5, located to the left of the positioning and assembly force measurement module 3. The installation positions of each module are shown in the diagram below. Figure 2 As shown. Specifically:

[0037] The structural diagram of the clamping module 1 is shown below. Figure 3As shown, its main body is a compliant amplification structure 8. Specifically, the compliant amplification structure 8 is an integrated structure, consisting of a bridge-type drive mechanism 9 and two U-shaped guide mechanisms 19 based on leaf-shaped hinges. The end where the U-shaped guide mechanism 19 is located is defined as the front end, and the end where the bridge-type drive mechanism 9 is located is defined as the rear end. The two U-shaped guide mechanisms 19 are symmetrically distributed about the Y-axis. At the bottom of the compliant amplification structure 8 in the clamping module 1, there are corresponding screw holes, which are connected and fixed to the rear end of the positioning and assembly force measurement module 3 by screws. The front ends of the two U-shaped guide mechanisms 19 are provided with symmetrical screw holes, which are used to connect and fix to the screw holes on the outer sides of the arrows at both ends of the positioning and assembly force measurement module 3 by bolts.

[0038] In this embodiment, the bridge drive mechanism 9 includes a front parallelogram mechanism 17, a rear parallelogram mechanism 10, a piezoelectric brake 12, a gasket 13, a first flexible hinge structure 16, a preload screw 15, and two end block structures 14. The two end block structures 14 are located at both ends, with a piezoelectric brake 12 in the middle. Gaskets 13 are provided at the contact points between the piezoelectric brake 12 and the end block structure 14, and are fixed by the preload screw 15. That is, the end block structures 14, piezoelectric brake 12, and gaskets 13 at both ends of the bridge drive mechanism 9 together form an I-shaped structure. The piezoelectric brake 12 is used to provide initial driving force and displacement for the movement of the piezoelectrically driven precision micro gripper, and the gaskets 13 are used to prevent the end face of the piezoelectric brake 12 from being damaged by concentrated load when the preload screw 15 is preloaded. The front parallelogram mechanism 17 and the rear parallelogram mechanism 10 are located between the two end block structures 14 and are symmetrically arranged on both sides of the piezoelectric brake 12 along the X-axis. The front parallelogram mechanism 17 is close to the zigzag guide mechanism 19 and includes four blocks. The middle part is a T-shaped block 18 composed of long and short sides. The four blocks are arranged in pairs and symmetrically arranged on both sides of the short side of the T-shaped block 18. One end of the block is connected to the end block structure 14, and the other end is internally connected to the T-shaped block 18. Each block is doubly connected through the first flexible hinge structure 16. The two ends of the long side of the T-shaped block 18 are respectively connected to the Z-shaped guide mechanism 19; the rear parallelogram mechanism 10 includes four blocks and a middle cuboid block 11. The four blocks are arranged in pairs, symmetrically at both ends of the middle cuboid block 11. One end of the block is connected to the end block structure 14, and the other end is internally connected to the middle cuboid block 11. Each block is doubly connected through the first flexible hinge structure 16; the parasitic motion generated by the front parallelogram mechanism 17 and the rear parallelogram mechanism 10 during movement can cancel each other out, which is used to make the end of the clamping module 1 generate an ideal displacement output in the target output direction; the Z-shaped guide mechanism 19 is used to realize a reliable guiding function, and can also effectively reduce the adverse effects of unnecessary displacement at the output end caused by the asymmetrical deformation of the input end of the gripper due to the action of the pre-tightening screw 15.

[0039] In this embodiment, the clamping module 1 inputs a corresponding voltage to the piezoelectric brake 12, causing the piezoelectric brake 12 to move. After the piezoelectric brake 12 moves, the compliant amplification structure 8 has a large amplification factor, which enables the end of the micro clamp to achieve ideal displacement output in the target output direction.

[0040] A schematic diagram of the clamping force measuring module 2 is shown below. Figure 4 As shown, the schematic diagram is as follows: Figure 5As shown, it includes a fixed guide beam 20 and a clamping force measuring strain gauge 21. The fixed guide beam 20 is an integrated structure with a thin cuboid block structure in the middle and thick cuboid block structures on both sides. The thin cuboid block structure and the thick cuboid block structures on both sides are doubly connected by a second flexible hinge structure 22. The clamping force measuring strain gauge 21 is attached to the lower part of the second flexible hinge structure 22 and is used to measure the clamping force. The second flexible hinge structure 22 is an over-constrained parallelogram hinge structure composed of two pairs of leaf-shaped flexible hinges. While retaining the "translational output" characteristics of the parallelogram mechanism, it improves the stiffness, stability and motion accuracy of the mechanism through redundant constraints. The clamping force measuring module 2 is set at the front end of the clamping module 1, located between the two Z-shaped guide mechanisms 19. Each of the thick cuboid block structures at both ends of the fixed guide beam 20 has a screw hole, which is connected to the long side of the T-shaped block 18 in the compliant amplification structure 8 by screws.

[0041] In this embodiment, when the precision device 6 is subjected to contact force, the clamping force measurement module 2 causes the over-constrained parallelogram mechanism of the fixed guide beam 20, which is composed of the second flexible hinge, to deform, resulting in a small displacement output by the clamping force measuring strain gauge 21. By connecting to the strain gauge, the clamping force can be measured. Based on the measured clamping force, the input voltage of the piezoelectric actuator 12 can be controlled to achieve effective clamping operation and reduce the damage to the clamped lens.

[0042] The top view and side view of the positioning and assembly force measurement module 3 are as follows: Figure 6 , Figure 7 As shown, this is an integrated arrow-shaped structure, including a V-groove positioning structure 23, a force-measuring mechanism 24, and a fixing mechanism 25. The V-groove positioning structure 23 and the force-measuring mechanism 24 are located on the body of the arrow-shaped structure, while the fixing mechanism 25 is located at the arrowhead. The V-groove positioning structure 23 is located at the front end, and the force-measuring mechanism 24 is located between the positioning V-groove positioning structure 23 and the fixing mechanism 25. All three are connected by a third flexible hinge structure 27 within the force-measuring mechanism 24. Specifically:

[0043] The V-groove positioning structure 23 has a V-groove on the side facing the force measuring mechanism 24. This V-groove, relying on its self-centering characteristics and bidirectional constraint, ensures that the clamping force is uniformly applied to the precision device 6 along a preset direction during clamping, avoiding stress concentration damage to the precision device 6. It also eliminates reference errors caused by positioning offset, improving the positioning accuracy of the precision device 6. A boss structure at the bottom of the V-groove is connected to one end of the third flexible hinge structure 27, and the other end of the third flexible hinge structure 27 is connected to the fixing mechanism 25. The force measuring mechanism 24 includes a positioning platform 26, the third flexible hinge structure 27, and an assembly force measuring strain gauge 28. The assembly force measuring strain gauge 28 is attached to the lower hinge of the third flexible hinge structure 27 for measuring assembly force. The positioning platform 26 is a thin sheet structure with an overall area larger than the precision device 6, used to place the precision device 6 and ensuring uniform force distribution on the precision device 6 during assembly, thus providing a certain degree of protection. The fixing mechanism 25 has two screw holes symmetrically arranged at each end. The two inner screw holes are connected to the base 5 by screws, and the two outer screw holes are connected to the front end of the two Z-shaped guide mechanisms 19 in the clamping module 1 by screws, which serves to fix the mechanism.

[0044] In this embodiment, the positioning and assembly force measurement module 3 inputs a corresponding voltage to the piezoelectric actuator 12, causing the piezoelectric actuator 12 to displace. After the compliant amplification structure 8 has a large amplification factor, the end of the precision micro gripper generates an ideal displacement output in the target output direction. The positioning accuracy of the object to be assembled is ensured by the V-groove positioning structure 23. After the gripping operation and fiber optic sensing positioning operation are completed, during the assembly process, the assembly force measuring strain gauge 28 in the force measuring mechanism 24 at the end of the positioning and assembly force measurement module 3 generates a small displacement. By connecting a strain gauge, the assembly force can be measured. Based on the measured assembly force, the robot motion can be controlled to effectively and safely complete the robot assembly motion and reduce the possibility of damage to the precision clamping device 6.

[0045] A schematic diagram of the structure of the fiber optic sensing module 4 is shown below. Figure 8As shown, the system includes an optical fiber fixing mechanism 29, a reflector 30, and a light probe 31. The light probe 31 is fixed to a pre-reserved rear end groove in the optical fiber fixing mechanism 29 by screws, and the reflector 30 is fixed to a pre-reserved front end groove in the optical fiber fixing mechanism 29 by screws. Specifically: the front end of the optical fiber fixing mechanism 29 is a polygonal beveled surface structure, which forms a groove for placing the reflector 30; the middle part of the optical fiber fixing mechanism 29 is a flat plate structure, with a cube block containing a through hole protruding from the left end of the flat plate structure for fixing the optical fiber sensing module 4 to the base 5; the rear end of the optical fiber fixing mechanism 29 has a block structure, the bottom of which is fixed to the base 5, and the middle part of the block structure at the rear end has a groove for placing the light probe 31, with a through hole on the side of the groove. Furthermore, the side of the polygonal beveled surface structure has a screw hole for fixing the reflector with screws.

[0046] In this embodiment, after the clamping mechanism 1 performs an effective clamping operation, before the assembly operation, the fiber optic sensing module 4 transmits light emitted from the light probe 31 to the assembly plane 7 via the reflector 30. The reflected light travels along the original path to the fiber end face and is received by the receiving fiber. The optical power of each receiving fiber is collected by the optical power meter, and the mathematical model established by the calculation software is used to solve the problem to determine the pose of the assembly plane relative to the fiber plane. The robot is then fine-tuned based on the determined pose, enabling the precision instruments to fit more precisely and closely, thus greatly improving the assembly accuracy of the precision instruments.

[0047] This embodiment provides a method for using a piezoelectric-driven precision micro gripper for two-degree-of-freedom force and three-degree-of-freedom pose measurement, including the following steps:

[0048] The first step is to place the precision component 6 to be assembled on the positioning platform 26 to complete the pre-assembly step.

[0049] The second step is to perform a clamping operation. A corresponding voltage is applied to the piezoelectric actuator 12 using a voltage signal input method, causing the piezoelectric actuator 12 to generate a micron-level initial displacement along the Y-axis, thus obtaining the piezoelectric initial displacement. The piezoelectric initial displacement is amplified by the compliant amplification structure 8 built into the clamping module 1, and the amplified displacement is transmitted to the end of the piezoelectric driven precision micro-clamping device to obtain the target displacement at the end of the piezoelectric driven precision micro-clamping device. The piezoelectric driven precision micro-clamping device is then controlled to move towards the pre-positioned assembly device until it contacts the surface of the precision device 6, generating an initial clamping force.

[0050] For clamping force measurement, when the precision device 6 is subjected to contact force, the over-constrained parallelogram mechanism of the fixed guide beam 20, which is composed of the second flexible hinge structure 22, will deform, causing the clamping force measuring strain gauge 21 to output a small deformation. The clamping force can be measured by connecting a strain gauge.

[0051] For clamping force control, PID control is adopted. Feedback is generated based on the measured clamping force, and the difference between the measured clamping force and the actual target clamping force is calculated. The feedback voltage is obtained through PID calculation and the input voltage of the piezoelectric brake 12 is controlled to achieve a safe and stable clamping state.

[0052] The third step involves performing fiber optic sensing and positioning after the clamping module 1 has achieved effective clamping operation and before the assembly operation. Through the fiber optic sensing module 4, the light emitted by the light probe 31 is reflected by the reflector 30 to the assembly plane 7. The reflected light travels back along the original path to the fiber end face and is received by the receiving fiber. The optical power of each receiving fiber is collected by the optical power meter, and the pose error of the assembly plane relative to the fiber plane is calculated by inverse kinematics. Based on the calculated pose error, the pose of the assembly robot is finely adjusted, so that the precision component 6 can fit more precisely and tightly with the assembly plane after the subsequent assembly operation, greatly improving the assembly accuracy of the precision component 6.

[0053] The fourth step involves performing a precision assembly operation after the fiber optic sensing positioning operation is completed. This involves controlling the precision component 6 to fit into the assembly plane 7. During the precision assembly operation, the assembly force measuring strain gauge 28 in the force measuring mechanism 24 at the end of the positioning and assembly force measuring module 3 after contact will produce a small displacement. By connecting a strain gauge, the assembly force can be measured. Based on the measured assembly force, the robot's movement can be controlled, thus effectively and safely completing the robot's assembly movement and reducing the possibility of damage to the clamped lens.

[0054] Fifth step: After the precision assembly operation is completed, by reducing the input voltage to the piezoelectric actuator 12, the clamping module 1 at the end of the piezoelectric drive micro gripper releases the precision component 6, and then the robot returns to zero, completing a single assembly operation.

[0055] The above embodiments are merely illustrative of the implementation methods of the present invention, but should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.

Claims

1. A piezoelectrically driven precision micro-gripper for two-degree-of-freedom force and three-degree-of-freedom pose measurement, characterized in that, The piezoelectric-driven precision micro gripper includes a gripping module (1), a gripping force measurement module (2), a positioning and assembly force measurement module (3), an optical fiber sensing module (4), a base (5), and precision components (6). A plane to be assembled (7) is provided directly above the piezoelectric-driven precision micro gripper. Using a right-hand coordinate system, the direction from the piezoelectric brake (12) in the gripping module (1) to the pre-tightening screw (15) is the positive X-axis, the direction perpendicular to the positioning platform (26) in the positioning and assembly force measurement module (3) is the positive Y-axis, and the direction perpendicular to the piezoelectric brake (12) to the V-groove positioning structure (23) in the positioning and assembly force measurement module (3) is the positive Z-axis. The positive X-axis is defined as the left, the positive Y-axis as the top, and the positive Z-axis as the front. The clamping module (1) is mounted on the positioning and assembly force measurement module (3) and located behind the positioning and assembly force measurement module (3); the clamping force measurement module (2) is mounted on the clamping module (1) and located between the two leaf-shaped hinge-based guide mechanisms (19) in the compliant amplification structure (8) of the clamping module (1); the positioning and assembly force measurement module (3) is mounted on the base (5); the precision device (6) is mounted on the positioning platform (26) of the positioning and assembly force measurement module (3); the fiber optic sensing module (4) is mounted on the base (5) and located to the left of the positioning and assembly force measurement module (3); specifically: The clamping module (1) is an integrated structure with a compliant amplification structure (8), consisting of a bridge-type drive mechanism (9) and two leaf-type guide mechanisms (19) based on leaf-type hinges. The clamping force measurement module (2) includes a fixed guide beam (20) and a clamping force measuring strain gauge (21); The positioning and assembly force measurement module (3) is an integrated arrow-shaped structure, including a V-groove positioning structure (23), a force measuring mechanism (24), and a fixing mechanism (25); the V-groove positioning structure (23) and the force measuring mechanism (24) are located on the arrow body, and the fixing mechanism (25) is located on the arrowhead; the V-groove positioning structure (23) is located at the front end, and the force measuring mechanism (24) is located between the positioning V-groove positioning structure (23) and the fixing mechanism (25); The fiber optic sensing module (4) includes a fiber optic fixing mechanism (29), a reflector (30), and a light probe (31); the light probe (31) is fixed in the rear groove of the fiber optic fixing mechanism (29), and the reflector (30) is fixed in the front groove of the fiber optic fixing mechanism (29).

2. The piezoelectrically driven precision micro-gripper for two-degree-of-freedom force and three-degree-of-freedom pose measurement according to claim 1, characterized in that, In the clamping module (1), the end where the zig-shaped guide mechanism (19) is located is defined as the front end and the end where the bridge-type drive mechanism (9) is located is defined as the rear end. The two zig-shaped guide mechanisms (19) are symmetrically distributed about the Y-axis. The front ends of the two zig-shaped guide mechanisms (19) are provided with symmetrical screw holes for connecting and fixing with the screw holes on the outer sides of the arrows of the positioning and assembly force measurement module (3).

3. The piezoelectrically driven precision micro-gripper for two-degree-of-freedom force and three-degree-of-freedom pose measurement according to claim 2, characterized in that, The bridge-type drive mechanism (9) includes a front parallelogram mechanism (17), a rear parallelogram mechanism (10), a piezoelectric brake (12), a gasket (13), a first flexible hinge structure (16), a preload screw (15), and two end block structures (14); specifically: A piezoelectric brake (12) is provided in the middle of the two end block structures (14). Gaskets (13) are provided at the contact points between the two ends of the piezoelectric brake (12) and the end block structure (14), and are fixed by pre-tightening screws (15). The front parallelogram mechanism (17) and the rear parallelogram mechanism (10) are located between the two end block structures (14) and are symmetrically arranged on both sides of the piezoelectric brake (12) along the X-axis. The front parallelogram mechanism (17) is close to the zigzag guide mechanism (19) and includes four blocks. The middle part is a T-shaped block (18) composed of a long side and a short side. The four blocks are arranged in pairs and symmetrically arranged on both sides of the short side of the T-shaped block (18). The long side of the T-shaped block (18) is connected to the zigzag guide mechanism (19). Each block is double-connected through the first flexible hinge structure (16). The rear parallelogram mechanism (10) includes four blocks and a middle cuboid block (11). The four blocks are arranged in pairs and symmetrically arranged at both ends of the middle cuboid block (11). Each block is double-connected through the first flexible hinge structure (16).

4. The piezoelectrically driven precision micro-gripper for two-degree-of-freedom force and three-degree-of-freedom pose measurement according to claim 3, characterized in that, In the clamping force measurement module (2): The fixed guide beam (20) is an integrated structure with a thin cuboid block structure in the middle and thick cuboid block structures on both sides. It is double-connected through the second flexible hinge structure (22). The clamping force measuring strain gauge (21) is attached to the bottom of the second flexible hinge structure (22) to measure the clamping force. The clamping force measuring module (2) is set at the front end of the clamping module (1) and is located between the two Z-shaped guide mechanisms (19). The thick cuboid block structures at both ends of the fixed guide beam (20) are provided with screw holes, which form a corresponding connection with the long side of the T-shaped block (18) in the compliant amplification structure (8).

5. The piezoelectrically driven precision micro-gripper for two-degree-of-freedom force and three-degree-of-freedom pose measurement according to claim 4, characterized in that, In the positioning and assembly force measurement module (3): The V-groove positioning structure (23), force measuring mechanism (24), and fixing mechanism (25) are connected by the third flexible hinge structure (27) in the force measuring mechanism (24); The V-groove positioning structure (23) has a V-groove on the side facing the force measuring mechanism (24). The bottom of the V-groove is connected to one end of the third flexible hinge structure (27), and the other end of the third flexible hinge structure (27) is connected to the fixing mechanism (25). The force measuring mechanism (24) includes a positioning platform (26), a third flexible hinge structure (27), and an assembly force measuring strain gauge (28). The assembly force measuring strain gauge (28) is attached to the lower hinge of the third flexible hinge structure (27) for measuring the assembly force. Precision devices (6) are placed on the positioning platform (26). The fixing mechanism (25) has screw holes at both ends for connecting to the base (5) and the front ends of the two Z-shaped guide mechanisms (19).

6. The piezoelectrically driven precision micro-gripper for two-degree-of-freedom force and three-degree-of-freedom pose measurement according to claim 5, characterized in that, In the fiber optic sensing module (4): The front end of the fiber fixing mechanism (29) is a polygonal beveled surface structure, which forms a groove for placing a reflector (30); the middle part of the fiber fixing mechanism (29) is a flat plate structure, and a cube block with a through hole is provided at the left end of the flat plate structure for fixing the fiber sensing module (4) on the base (5); the rear end of the fiber fixing mechanism (29) is provided with a block structure, which is fixedly connected to the base (5) at the rear end, and a groove is provided in the middle of the block structure for placing a light probe (31).

7. A method of using a piezoelectrically driven precision micro-gripper for two-degree-of-freedom force and three-degree-of-freedom pose measurement as described in any one of claims 1-6, characterized in that, Includes the following steps: The first step is to place the precision component (6) to be assembled on the positioning platform (26) to complete the pre-assembly step; The second step is to perform a clamping operation; to make the piezoelectric actuator (12) generate a micron-level initial displacement along the Y-axis direction, thus obtaining the piezoelectric initial displacement; The piezoelectric initial displacement is amplified by the compliant amplification structure (8) of the clamping module (1) and transmitted to the end of the piezoelectric driven precision micro clamp to obtain the target displacement of the end of the piezoelectric driven precision micro clamp. The piezoelectric driven precision micro clamp is controlled to move towards the precision device (6) that has completed the prepositioning until the piezoelectric driven precision micro clamp contacts the surface of the precision device (6) and generates the initial clamping force. For clamping force measurement, when the precision device (6) is subjected to contact force, the deformation is output by the clamping force measuring strain gauge (21), and the clamping force is measured by connecting the strain gauge. For clamping force control, PID control is adopted. Feedback is generated based on the measured clamping force to control the input voltage of the piezoelectric brake (12) and achieve a stable clamping state. The third step is to perform fiber optic sensing positioning before assembly. The light emitted by the light probe (31) is reflected by the reflector (30) to the plane to be assembled (7). The reflected light goes back to the fiber end face through the original path. The optical power is collected and the pose error of the plane to be assembled (7) relative to the fiber plane is calculated. The pose is then finely adjusted so that the precision device (6) can fit tightly with the plane to be assembled (7). The fourth step is to perform precision assembly operations; after the precision component (6) and the assembly plane (7) are in contact, the assembly force measuring strain gauge (28) in the force measuring mechanism (24) will be displaced, and the assembly force will be measured by connecting the strain gauge. The control will be based on the measured assembly force. In the fifth step, after the precision assembly operation is completed, the clamping module (1) releases the precision component (6) by reducing the input voltage to the piezoelectric brake (12), thus completing a single assembly operation.

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